N-(propynyl)-2-(thiazole) sulfenamides as rubber accelerators



United States Patent 18 Claims. (Cl. 260-795) This application is a division of my copending application Serial No. 739,989, filed June 5, 1958, now Patent No. 3,020,287.

This invention relates to a new class of chemical compounds and to the application of these substances to the acceleration of rubber vulcanization.

Certain thiazole sulfenamides have been produced by reacting an alkylamine with mercaptobenzothiazole in the presence of an oxidizing agent such as chlorine. For example, n-butylamine has been condensed with Z-mercaptobenzothiazole in the presence of chlorine to produce N-nbutyl-Z-benzothiazolesulfenamide, a low melting solid, which decomposes upon standing at room temperature. Although this prior sulfenamide, when freshly prepared, is a rubber vulcanization accelerator having moderately delayed-action properties, its potency gradually diminishes when it is stored.

During the last few years in the rubber industry the channel carbon blacks have been increasingly replaced by the newer reinforcing oil furnace blacks in pneumatic tire tread compositions. Several of the new furnace blac ks, e.g., HAP, ISAF and SAP blacks, have become popular because they impart much longer tread life to tires than did the channel blacks. Whereas the channel blacks were acidic in reaction, the new furnace blacks are alkaline, displaying pH values above 7.0. Perhaps partly because of their alkalinity the new furnace blacks have been ditficult to handle in modern high speed rubber processing equipment, because they tend to make rubber stocks scorchy, the stocks tending to set up or precure before the end of the mechanical working of the stocks during processing in Banbury mixers, mills, calenders and extruders. A scorched stock, of course, must be scrapped. As typical of many prior accelerators, the butylbenzothiazole sulfenamide mentioned above is not sufficiently delayed in action to function in a commercially acceptable manner as the accelerator in a reinforcing oil furnace black tread stock.

It is an object of the present invention to provide a new class of thiazole sulfenamides, possessing excellent chemical stability and unique rubber vulcanization accelerating characteristics. It is also an object to provide improved rubber compositions or stocks free from tendency to scorch during factory processing operations. A further object is to provide an improved method of vulcanizing sulfur-vulcanizable rubbers. Another object is to provide improved vulcanized rubber compositions. The above and further objects will become apparent in the description of the invention which follows.

The objects of the invention are realized through the discovery of a new class of thiazole sulfenamides, the N- 3 ,223,684 Patented Dec. 14, 1965 (propynyl)-2-(thiazole) sulfenamides of the following formula:

Rr-C-S III A R, and R are each hydrogen or an alkyl radical, or together with the ethylene nucleus to which they are attached they form an alicyclic or aromatic ring. R is hydrogen or an alkyl radical, and R is a hydrocarbon or substituted hydrocarbon radical, with the proviso that R and R together with the carbon atom to which they are attached, can constitute a cyclic hydrocarbon radical. A preferred group in the new class of compounds is one in which R is methyl or ethyl or in which R and R join to form a cycloalkyl radical.

The new sulfenamides can be made by forming the monochloramine of a non-aromatic primary amine having an ethynyl group in the alpha position, and reacting the monochloramine with a Z-rnercaptothiazole. Alternatively, a Z-mercaptothiazole can be condensed with an appropriate primary acetylenic amine in the present of an oxidizing agent. Suitable Z-mercaptothiazoles include, for example, mercaptothiazole, mercaptobenzothiazole, 4,5- dimethyl-mercaptothiazole, 4 ethyl mercaptothiazole, mercaptonaphthothiazole, mercapto-5,6,7,8 tetrahydrobenzothiazole, mercapto nitrobenzothiazole, mercaptoalkylbenzothiazoles, mercapto arylbenzothiazoles, mercapto methylbenzothiazoles, mercapto dimethylbenzothiazoles, mercapto-phenylbenzothiazoles, mercapto-tolylbenzothiazoles, and mercapto-chlorobenzothiazole. Appropriate acetylenic amines include, for example, 1,1-dimethylpropynylamine (i.e., 3-amino-3-methyl-l-butyne), ethynylcyclopentylamine and ethynylcyclohexylamine. Other suitable amines include the following substituted propynylamines responding to the formula in which R is hydrogen and R is chosen from the following list of radicals or in which both R and R are chosen from the following list of radicals:

Methyl n-Propyl n-Butyl t-Butyl Any amyl Any heptyl Any nonyl Any dodecyl Any octadecyl Cyclopentyl l-methylcyclopentyl Phenyl l-methylcyclohexyl p-Chlorophenyl Beta-naphthyl Anthranyl Tolyl Allyl Dimethylallyl Octadecenyl Ethyl Isopropyl Sec-butyl Isobutyl Any hexyl Any octyl Any decyl Any hexadecyl Eicosyl Cyclohexyl Benzyl o-Hydroxyphenyl o-Chlorophenyl Alpha-naphthyl m-Chlorophenyl Phenanthryl Biphenylyl Methallyl Diethylallyl Diallylmethyl Additional examples of suitable amines in which R and R join to form a cyclic hydrocarbon radical include the following:

Ethynylcyclobutylamine Ethynylcyclopropylamine Ethynylcycloheptylamine Ethynylcyclooctylamine Ethynylcyclobutenylamine Ethynylcyclopentenylamine Ethynylcyclohexenylamine Ethynylcycloheptenylamine Ethyny-lcyclooctenylamine Ethynylcyclodecylamine Ethynylcyclodecenylamine Ethynylcyclohexadienylamine Ethynylcycloheptadienylamine Ethynylcyclooctadienylarnine Ethynylcycloheptatrienylamine Ethynylcyclooctatrienylamine The above amines can be prepared from the appropriate carbonyl compound in accordance with the following series of reactions:

The invention is illustrated by the following examples.

EXAMPLE 1 The acetylenic amine, 1,1-dimethyl-Z-propynylamine, was obtained in accordance with the reactions set out above from acetone as the basic starting material. This amine boiled at 78.581 C. at atmospheric pressure and had a refractive index, n of 1.4260. The amine was converted to a thiazole sulfenamide as follows:

Reactants:

0.15 mole 2-mercaptobenzothiazole 0.15 mole sodium hydroxide 47 ml. water 0.285 mole 1,1-dimethyl-2-propynylamine 150 ml. 1 molar K1 solution The sodium hydroxide and then the thiazole were dissolved in the water. The amine was mixed with the mercaptobenzothiazole salt solution at 25-30 C., and then the KI solution was gradually added with stirring at 2530 C. Then the reaction mixture was poured into 500 ml. of ice and water, and a solid, light green precipitate separated. The precipitate was'washed with water several times and air-dried. Since the crude product melted at ISO-155 C., it was extracted with diethyl ether to yield 16.8 grams of an ether soluble substance (36% of theory for the desired sulfenamide), which after recrystallization from a methanol-water mixture melted at 110111.5 C. This product, N-(1,1-dimethyl-2-propynyl)-2-benzothiazole sulfenamide, a very stable solid, was analyzed, with the following results:

Percent Percent Nitrogen Sulfur Calculated from the formula 11.28 25.82 Found 10.97 25.62

4 EXAMPLE 2 Starting with methyl ethyl ketone, l-methyl-l-ethyl-Z- propynylamine was obtained by the method set out above. This amine boiled at 50-52 C. at mm. The refractive index, n of the amine was in the range of 1.4345 to 1.4360 (several preparations were made). The amine was converted to a thiazole sulfenamide by the method of Example 1.

Reactants:

0.1 mole Z-mercaptobenzothiazole 0.20 mole sodium hydroxide 47 ml. water 0.31 mole 1-methyl-1-ethy1-2-propynylamine ml. 1 molar K1 solution Results Yield 100% crude product, 59.5% of recrystallized product, N-( l-methyl-l -ethyl-2-propynyl -2-benzothiazole sulfenamide, a very stable solid, melting at 94.595 C., and analyzing as follows:

Percent Sulfur 24.43 24.46

Percent Nitrogen Calculated from the formula 10.68 Found 10.28

EXAMPLE 3 The amine was converted to a thiazole sulfenamide by the method of Example 1 in a yield of 86%. The purified product, N-( 1-methyl-1-isobutyl-2-propynyl)-2-benzothiazole sulfenamide, a stable solid, melted at 124.5126.5 C. and analyzed as follows:

Percent Percent Sulfur Nitrogen Calculated from the formula 22.05 9.64 Found 22.00 9.44

EXAMPLE 4 Starting with methyl n-hexyl ketone, l-me-thyl-l-nhexyl-2-propynylamine was obtained by the above-described method. This amine boiled at 77.5" C. at 10.9 mm. and possessed a refractive index, n of 1.4433.

The amine hydrochloride melted at 155.5-156.5 C. and analyzed as follows:

Percent Percent Nitrogen Chlorine Calculated from the formula 7.39 18.71 Found 7.24 18.63

The amine was converted to a thiazole sulfenamide by the method of Example 1 in a yield of 71%. The purified product, N-( 1-methyl-1-n-hexyl-2-propynyl -2-benzothiazole sulfenamide, a stable solid, melted at 92.594.5 C.

and analyzed as follows:

Percent Percent Sulfur Nitrogen Calculated from the formula 20.19 8.80 Found 20.40 8.72

EXAMPLE 5 Starting with cyclohexanone, 1 ethynyl cyclohexylamine was obtained by the above general method. This amine boiled at 5663 C. at 14 mm. and possessed a refractive index, 11 of 1.4817. The amine hydrochloride melted at 270.5 C. and analyzed as follows:

Percent Percent Nitrogen Chlorine Calculated from the formula 8.78 22.25 Found 8.70 22.01

The amine was converted to a thiazole sulfenamide by the method of Example 1 in a yield of 47%. The purified product, N(l-ethynylcyclohexyl)-2-benzothiazole sulfenamide, a very stable solid, melted at 1101l2 C. and analyzed as follows:

Percent Percent Sulfur Nitrogen Calculated from the formula 22.00 9.70

Found 21.70 9.33

Example 6 Reactants:

grams (0.36 mole) l-methyl-1-ethyl-2-propyr1ylamine 7.2 grams (0.18 mole) sodium hydroxide ml. water ml. ethyl alcohol 10.3 grams (0.07 mole) 2-mercapto-4,5-dimethylthiazole ml. 1 molar K1 solution The sodium hydroxide was dissolved in the water, and the mercaptothiazole was dissolved in this caustic solution. The amine was added, and the alcohol was mixed in to insure a homogeneous solution. Then the K1 so lution was added dropwise at 26 C. with stirring during 90 minutes. No precipitate was apparent until 10 ml. of Water was added, and then a small amount of precipitate appeared. The reaction vessel was stored at 5 C. overnight in an icebox. The considerable precipitate thereby obtained was separated by filtration and was airdried. The reaction product was obtained in a yield of 12.0 grams, 71% of theory, melting at 9396 C. After recrystallization from a methanol-water mixture the product, N (1 methyl-1-ethyl-2-propynyl)-2- (4,5-dimethylthiazole) sulfenamide, a very stable crystalline solid, melted at 92.5-94.5 C. and analyzed as follows:

Percent Percent Sulfur Nitrogen Calculated from the formula 26.69 11.66 Found 26.75 11.48

Additional examples of the sulfenamides of the invention are produced from the appropriate amines and mercaptothiazoles, and are listed as follows:

N( l-methyl-l-ethyl-2-propynyl -2thiazole sulfenamide N( l-ethyll-isobutyl-Z-propynyl -2-( 4-ethylthiazole) sulfenamide N( 1,1-diethyl-2-propynyl)-2-(6-phenylbenzothiazole) sulfenamide N( l n-propyl-1-n-amyl-2-propynyl) -2- (4-p-tolylbenzothiazole) sulfenamide N( l-methyl-1-eicosyl-2-propynyl)-2-(6-chlorobenzothiazole) sulfenamide N-[1-ethyl-1-( l-methylcyclopentyl) -2-propynyl] -2- (5,6,7,S-tetrahydrobenzothiazole) sulfenamide N( 1-methyl-1-allyl-2-propynyl) -2naphthobenzothiazole sulfenamide N( l-methyl-1-t-dodecyl-2-propynyl)-2-(6-nitrobenzothiazole) sulfenamide N( 1-methyl-1-benzyl-2-propynyl) -2-benzothiazole sulfenamide N( l-ethynylcyclopentyl -2- 4,6-dimethylbenzothiazole) sulfenamide 6 N(l-ethynylcyclobutenyl)-2-Jenzothiazole sulfenamide N( l-ethynylcyclohexadienyl -2-benzothiazole sulfenamide N- 1-ethynylcycloheptatrienyl -2-benzothiazole sulfenamide These additional examples have properties equivalent to those of the preceding examples described in detail hereinabove.

The sulfenamides of the invention are effective delayedaction vulcanization accelerators in any of the sulfurvulcanizable diene rubbers including, without limitations, natural rubber, various synthetic rubbers such as SBR (butadiene-styrene), BR, IR, ABR, PBR, SIR, neoprene (polychloroprene or CR), butyl rubber (HR) and suitable mixtures thereof. (The abbreviations are in accord with the ASTM Designation: D1418-56T.) The usual curing temperatures employed by the art can be utilized, suitably in the range from about 250 to about 400 F. The amount of accelerator employed will depend on the particular rubber composition being vulcanized, as will be understood by one skilled in the art, for example, between 0.05 and 5 parts by weight per one hundred parts of the rubber (phr.). The sulfenamides of the invention are effective accelerators of vulcanization by free sulfur or by a vulcanizing agent of the su1fur-donor type, including without limitation various known phenol polysulfides including the alkyl derivatives thereof, the Xanthogen polysulfides, the thiuram disulfides and other polysulfides, various amine polysulfides including the dialkylamine polysulfides, heterocyclic amine polysulfides and reaction products of primary amines with excess sulfur. The sulfenamides are useful in all other types of rubber stocks besides tire tread stocks and can be mixed with the rubber on a rubber mill, in a Banbury, in a solvent rubber cement, in latex or water dispersion or in any other manner known to the art of mixing a compounding ingredient with a rubber.

The sulfenamides of Examples 1 and 2 were tested as delayed-action vulcanization accelerators in a natural rubber tire tread stock reinforced by a reinforcing oil furnace black in accordance with Formula A.

The two test stocks in accordance with Formula A were each thoroughly mixed in the usual manner in a rubber mill. The Mooney Scorch Test (I. V. Weaver, Rubber Age, volume 48, pages 8995 (1940)) was applied to samples of the two stocks, and the test results in minutes are shown in Table I.

TABLE I.MOONEY SCORCH AT 250 F.

Initial 10 Point Rise Stock Containing Sulfenamide of Example 1 32 40 Sulfenamide of Example 2 30 40 The results shown in Table I indicate the new sulfenamides to be very effective delayed-action accelerators,

7 providing complete freedom from scorch during normal factory processing of a natural rubber furnace black tire tread stock containing one of them. Other portions of the two stocks were vulcanized at 280 F., and the following normal and aged tensile data were obtained (p.s.i. means pounds per square inch):

TABLE II.NO RMAL PHYSICAL PROPERTIES Stock Containing Sulfenamide of- Example 1 Example 2 Modulus at 300% (p.s.i.):

30 minute cure- 1, 300 1, 200 45 minute cure- 1, 875 1, 700 60 minute cure 2, 075 1, 875 90 minute cure 2, 225 2, 100 Modulus at 400% (p s 1 30 minute cure- 2, 250 2, 175 45 minute cure 2, 850 2, 800 60 minute cure 3, 250 3, 050 90 minute cure 3, 450 3, 375 Tensile strength (p.s

30 minute cure- 3, 350 3, 400 45 minute cure- 4, 200 3, 975 60 minute cure 4, 225 4, 000 90 minute cure 3, 975 4, 225 Elongation (Percent at Break) 30 minute cure 485 535 45 minute cure 510 530 60 minute cure 470 490 90 minute cure 460 485 PROPERTIES AFTER AGING 2 DAYS AT 212 F. (OVEN) Modulus at 300% (p.s.i.);

80 minute cure. 1, 575 1, 500 45 minute cure 1, 925 1, 775 1, 950 1, 900

2, 575 2, 675 2, 300 2, 525 2, 000 2, 325 90 minute cure- 1, 850 2, 050 Elongation (Percent at 30 minute cure 425 450 45 minute cure 360 400 60 minute cure- 310 355 90 minute cure 265 295 Table II shows that the new accelerators impart good physical properties to natural rubber tread stocks and that these properties are substantially maintained after a severe aging period.

In a similar manner the sulfenamides of Examples 1 and 2 were tested as delayed-action accelerators in a synthetic rubber tire tread stock in accordance with Formula B.

Formula B Parts by Ingredients weight SBR (LTP)* 100 HAF carbon black 48 Zinc oxide 3 Petroleum oil (naphthenic) 8 Stearic acid 2 Antioxidant 0.6

Sulfur 2 Accelerator 1.2

*Rubbery butadiene-styrene copolymer prepared by emulsion polymerization at 41 ll.

The two test stocks in accordance with Formula B were each thoroughly mixed in the usual manner in a rubber mill. Results of the Mooney Scorch Test are shown in Table III.

TABLE III.MOONEY SCOROH AT 265 F.

Initial 10 Point Rise Stock Containing- Sulfenamide of Example 1 40 40 Sulfenamide of Example 2 40 40 Table III illustrates the high degree of safety from scorch aflorded by use of the new sulfenamides in a conventional type of synthetic rubber tire tread stock. Other portions of the two stocks were cured at 280 F., and the following normal and aged tensile data were obtained:

TABLE IV.NORMAL PHYSICAL PROPERTIES PROPERTIES AFTER AGING 2 DAYS AT 212 F. (OVEN) Modulus at 400%:

45 minute cure 1, 275

60 minute cure- 2, 300 425 minute cure 2, 725 Tensile strength:

45 minute cure 2, 425

60 minute cure- 3, 325 2, 800

90 minute cure 2, 950 3, 275 Elongation:

45 minute cure 625 60 minute cure- 540 645 90 minute cure 355 465 No cure.

Table IV shows that the new sulfenarnides are quite delayed-action in a conventional SBR tread stock but that they gave a good cure in 90 minutes at 280 F., and that the cured stock withstood aging extremely Well.

The novel sulfenamides of Examples 3, 4 and 5 were tested as delayed-action accelerators in the natural rubber stock of Formula A. Results of the Mooney Scorch Test are given in Table V.

TABLE V.--MOONEY SCORCH AT 250 F.

Initial 10 Point Rise Stock Containing- Sulfenamide of Example 3-. 27. 0 40 Sulfenamide of Example 4 29. 0 40 Sultan-amide of Example 5 29. 5 40 Table V shows that the sulfenamides of Examples 3, 4 and 5 are quite similar to those of Examples 1 and 2 in providing freedom from scorch of natural rubber furnace black tire tread stocks during normal factory processing. Other portions of the three stocks were vulcanized at 9 280 F., and the following normal and aged tensile data were obtained:

TABLE VI.NORMAL PHYSICAL PROPERTIES Stock Containing Sulfenamide of- Example 3 Example 4 Example 5 Modulus at 300%:

45 minute cure. 1, 925 1, 950 1, 975

60 minute cnre 2, 200 2, 125 2,075

90 minute cure 2, 325 2, 250 2, 350 Tensile strength:

45 minute cure 4,025 4, 050 4, 125

60 minute cure. 4, 150 4, 225 4, 000

90 minute cure 4, 050 4, 025 4, 275 Elongation:

45 minute cure 540 540 540 60 minute cure. 520 530 510 90 minute cure- 480 490 500 PROPERTIES AFIE R AGING 2 DAYS AT 212 F.

Modulus at 300%:

45 minute cure 1, 750 l, 800 1, 800

60 minute cure. 1, 900 2,000 1,950

90 minute cure. 2, 200 2, 225 2, 250 Tensile strength:

45 minute cure 2, 600 2, 475 2, 450

60 minute cure 2, 525 2, 575 2, 525

90 minute cure. 2, 350 2, 375 2, 250 Elongation:

45 minute cure 410 400 400 60 minute cure 380 380 400 90 minute cure .310 310 300 TABLE VII.MOONEY SOORCH AT 275 F.

Initial Point Rise Stock containing- Sulfenamide of Example 3 23 40 Sulfenamide of Example 4 26 40 Table VII shows that even at the high testing temperature of 275 F. the new accelerators possess good delayed action. Other portions of the two stocks were cured at 300 F., and the following normal and aged tensile data were obtained:

TABLE VIII-NORMAL PHYSICAL PROPERTIES Stock Containing Sulienamide of- Example 3 Example 4 Modulus at 300%:

30 minute cure it 250 175 45 minute cure. 1, 125 1, 000

60 minute cure l, 700 1,650 Tensile strength:

30 minute cure 650 400 45 minute cure- 3, 300 3,000

60 minute cure 3, 650 3, 625 Elongation:

30 minute cure -2 870 1,040

680 670 60 minute cure 550 560 PROPERTIES AFTER AGING 2 DAYS AT 212 F.

Modulus at 300%:

30 minute cure 1, 000 925 45 minute eure 2, 325 2, 250

60 minute cure 2, 800 2, 800 Tensile strength:

30 minute cure 2, 750 2,600

45 minute cure. 3, 475 3, 5

60 minute cure 3, 300 3, 375 Elongation:

30 minute cure 650 680 45 minute cure 430 420 60 minute cure 350 370 Table VIII shows that the new sulfenamides were quite delayed in action in a conventional SBR tread stock but that they gave good cures in 45 and 60 minutes at 300 F., and that the cured stocks withstood aging remarkably well.

I claim:

1. A vulcanizable composition comprising a sulfur vulcanizable diene rubber, sulfur and between 0.05 and 5 phr. of an N-(propynyl)-2-(thiazole) sulfenamide selected from the class consisting of those sulfenamides having one of the following formulas:

o-s-n-o-ozon l s H X wherein R is a member selected from the group consisting of hydrogen and lower alkyl; R; is a member selected from the group consisting of alkyl of no more than 20 carbon atoms, alkenyl of no more than 18 carbon atoms, cycloalkyl of no more than 7 carbon atoms and hydrocarbon aryl of no more than 14 carbon atoms;

is a member of the group consisting of ethynylcycloalkyl and ethynylcycloalkenyl containing no more than 12 carbon atoms, ethynylcycloalkadienyl and ethynylcycloalkatrienyl containing no more than 10 carbon atoms; and the valences of the carbon atoms in the 4- and 5-positions of the thiazole ring are satisfied by a member selected from the group consisting of hydrogen, methyl, ethyl and residues of carbocyclics, said carbocyclics containing no more than 13 carbon atoms and being a member selected from the group consisting of unsubstituted naphtho, unsubstituted benzo, 5, 6, 7, 8-tetrahydrobenzo, nitrobenzo, alkylbenzo, methylbenzo, dirnethylbenzo, phenylbenzo, tolylbenzo and chlorobenzo.

2. Method of vulcanizing rubber comprising heating the composition of claim 1.

3. A vulcanizable composition comprising a sulfurvulcanizable diene rubber, sulfur and between 0.05 and 5 phr. of a compound of the structure wherein R is a lower alkyl and R is an alkyl of no more than 20 carbon atoms.

4. Method of vulcanizing rubber comprising heating the composition of claim 3.

5. A vulcanizable composition comprising a sulfurvulcanizable diene rubber, sulfur and between 0.05 and 5 phr. of a compound of the structure wherein is ethynylcycloalkyl of no more than 12 carbon atoms.

6. Method of vulcanizing rubber comprising heating the composition of claim 5.

7. A vulcanizable composition comprising a sulfurvulcanizable diene rubber, sulfur and between 0.05 and phr. of a compound of the structure wherein R is a lower alkyl and R is a cycloalkyl of no more than 7 carbon atoms.

8. Method of vulcanizing rubber comprising heating the composition of claim 7.

9. A vulcanizable composition comprising a sulfurvulcanizable diene rubber, sulfur and between 0.05 and 5 phr. of N-(1,l-dimethyl-Z-propynyl)-2-benzothiazo1e sulfenarnide.

10. Method of vulcanizing rubber comprising heating the composition of claim 9.

11. A vulcanizable composition comprising a sulfurvulcanizable diene rubber, sulfur and between 0.05 and 5 phr. of N- (l-methyl-1-ethy1-2-propynyl)-2-benzothiazole sulfenamide.

12. Method of vulcanizing rubber comprising heating the composition of claim 11.

13. A vulcanizable composition comprising a sulfurvulcanizable diene rubber, sulfur and between 0.05 and 5 phr. of N-(l-methyl-1-isobutyl-2-propynyl)-2-benzothiazole sulfenamide.

14. Method of vulcanizing rubber comprising heating the composition of claim 13.

15. A vulcanizable composition comprising a sulfurvulcanizable diene rubber, sulfur and between 0.05 and 5 phr. of N-(l-methyl-l-n-hexyl-Z-propynyl)-2-benzothiazole sulfenamide.

16. Method of vulcanizing rubber comprising heating the composition of claim 15.

17. A vulcanizable composition comprising a sulfurvulcanizable diene rubber, sulfur and between 0.05 and 5 phr. of N-(l-ethynylcyclohexyl)-2-benzothiazole sulfenamide.

18. Method of vulcanizing rubber comprising heating the composition of claim 17.

References Cited by the Examiner UNITED STATES PATENTS 2,769,010 10/1956 DAmico 260302 2,875,208 2/1959 DAmico 260-306.61

JOSEPH L. SCHOFER, Primary Examiner.

M. LIEBMAN, Examiner. 

1. A VULCANIZABLE COMPOSITION COMPRISING A SULFUR VULCANIZABLE DIENE RUBBER, SULFUR AND BETWEEN 0.05 AND 5 PHR. OF AN N-(PROPYNYL)-2-(THIAZOLE) SULFENAMIDE SELECTED FROM THE CLASS CONSISTING OF THOSE SULFENAMIDES HAVING ONE OF THE FOLLOWING FORMULAS: 